'\" te
.\"  Copyright (c) 2002 Sun Microsystems, Inc.  All Rights Reserved.
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
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.TH DDI_DMA_BUF_BIND_HANDLE 9F "Jan 18, 2020"
.SH NAME
ddi_dma_buf_bind_handle \- binds a system buffer to a DMA handle
.SH SYNOPSIS
.nf
#include <sys/ddi.h>
#include <sys/sunddi.h>



\fBint\fR \fBddi_dma_buf_bind_handle\fR(\fBddi_dma_handle_t\fR \fIhandle\fR, \fBstruct buf *\fR\fIbp\fR,
     \fBuint_t\fR \fIflags\fR, \fBint (*\fR\fIcallback\fR)(caddr_t), \fBcaddr_t\fR
     \fIarg\fR, \fBddi_dma_cookie_t *\fR\fIcookiep\fR, \fBuint_t *\fR\fIccountp\fR);
.fi

.SH INTERFACE LEVEL
illumos DDI specific (illumos DDI).
.SH PARAMETERS
.ne 2
.na
\fB\fIhandle\fR\fR
.ad
.RS 12n
The \fBDMA\fR handle previously allocated by a call to
\fBddi_dma_alloc_handle\fR(9F).
.RE

.sp
.ne 2
.na
\fB\fIbp\fR\fR
.ad
.RS 12n
A pointer to a system buffer structure (see \fBbuf\fR(9S)).
.RE

.sp
.ne 2
.na
\fB\fIflags\fR\fR
.ad
.RS 12n
Valid flags include:
.sp
.ne 2
.na
\fB\fBDDI_DMA_WRITE\fR\fR
.ad
.RS 22n
Transfer direction is from memory to I/O
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_READ\fR\fR
.ad
.RS 22n
Transfer direction is from I/O to memory
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_RDWR\fR\fR
.ad
.RS 22n
Both read and write
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_REDZONE\fR\fR
.ad
.RS 22n
Establish an \fBMMU\fR redzone at end of the object.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_PARTIAL\fR\fR
.ad
.RS 22n
Partial resource allocation
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_CONSISTENT\fR\fR
.ad
.RS 22n
Nonsequential, random, and small block transfers.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_STREAMING\fR\fR
.ad
.RS 22n
Sequential, unidirectional, block-sized, and block-aligned transfers.
.RE

.RE

.sp
.ne 2
.na
\fB\fIcallback\fR\fR
.ad
.RS 12n
The address of a function to call back later if resources are not available
now. The following special function addresses may also be used.
.sp
.ne 2
.na
\fB\fBDDI_DMA_SLEEP\fR\fR
.ad
.RS 20n
Wait until resources are available.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_DONTWAIT\fR\fR
.ad
.RS 20n
Do not wait until resources are available and do not schedule a callback.
.RE

.RE

.sp
.ne 2
.na
\fB\fIarg\fR\fR
.ad
.RS 12n
Argument to be passed to the callback function, \fIcallback\fR, if such a
function is specified.
.RE

.sp
.ne 2
.na
\fB\fIcookiep\fR\fR
.ad
.RS 12n
A pointer to the first  \fBddi_dma_cookie\fR(9S) structure.  This should
be left as \fBNULL\fR in new callers.
.RE

.sp
.ne 2
.na
\fB\fIccountp\fR\fR
.ad
.RS 12n
Upon a successful return, \fIccountp\fR points to a value representing the
number of cookies for this \fBDMA\fR object.  This can
be left as \fBNULL\fR in new callers.  The cookie count can be obtained
by calling \fBddi_dma_ncookies\fR(9F).
.RE

.SH DESCRIPTION
\fBddi_dma_buf_bind_handle()\fR allocates \fBDMA\fR resources for a system
buffer such that a device can perform \fBDMA\fR to or from the buffer.
\fBDMA\fR resources are allocated considering the device's \fBDMA\fR attributes
as expressed by \fBddi_dma_attr\fR(9S) (see \fBddi_dma_alloc_handle\fR(9F)).
.sp
.LP
\fBddi_dma_buf_bind_handle()\fR allocates and associates a number of
\fBDMA\fR cookies with \fIhandle\fR.  To get the total number of
cookies, callers should use the \fBddi_dma_ncookies\fR(9F) function. To
get all of the cookies, callers should use the
\fBddi_dma_cookie_iter\fR(9F) or \fBddi_dma_cookie_get\fR(9F) functions.
Callers should pass \fBNULL\fR for \fIcookiep\fR and \fIccountp\fR.
These values are required if using the deprecated
\fBddi_dma_nextcookie\fR(9F) interface, in which case \fIcookiep\fR is
filled in with the first \fBddi_dma_cookie\fR(9S) structure.

.sp
.LP
When a \fBDMA\fR transfer completes, the driver should free up system \fBDMA\fR
resources by calling \fBddi_dma_unbind_handle\fR(9F).
.sp
.LP
The \fIflags\fR argument contains information for mapping routines.
.sp
.ne 2
.na
\fB\fBDDI_DMA_WRITE\fR, \fBDDI_DMA_READ\fR, \fBDDI_DMA_RDWR\fR\fR
.ad
.sp .6
.RS 4n
These flags describe the intended direction of the \fBDMA\fR transfer.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_STREAMING\fR \fR
.ad
.sp .6
.RS 4n
This flag should be set if the device is doing sequential, unidirectional,
block-sized, and block-aligned transfers to or from memory. The alignment and
padding constraints specified by the \fBminxfer\fR and \fBburstsizes\fR fields
in the \fBDMA\fR attribute structure, \fBddi_dma_attr\fR(9S) (see
\fBddi_dma_alloc_handle\fR(9F)) is used to allocate the most effective hardware
support for large transfers.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_CONSISTENT\fR \fR
.ad
.sp .6
.RS 4n
This flag should be set if the device accesses memory randomly, or if
synchronization steps using \fBddi_dma_sync\fR(9F) need to be as efficient as
possible. I/O parameter blocks used for communication between a device and a
driver should be allocated using \fBDDI_DMA_CONSISTENT\fR.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_REDZONE\fR \fR
.ad
.sp .6
.RS 4n
If this flag is set, the system attempts to establish a protected red zone
after the object. The \fBDMA\fR resource allocation functions do not guarantee
the success of this request as some implementations may not have the hardware
ability to support a red zone.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_PARTIAL\fR \fR
.ad
.sp .6
.RS 4n
Setting this flag indicates the caller can accept resources for part of the
object. That is, if the size of the object exceeds the resources available,
only resources for a portion of the object are allocated. The system indicates
this condition returning status \fBDDI_DMA_PARTIAL_MAP\fR. At a later point,
the caller can use \fBddi_dma_getwin\fR(9F) to change the valid portion of the
object for which resources are allocated. If resources were allocated for only
part of the object, \fBddi_dma_addr_bind_handle()\fR returns resources for the
first \fBDMA\fR window. Even when \fBDDI_DMA_PARTIAL\fR is set, the system may
decide to allocate resources for the entire object (less overhead) in which
case \fBDDI_DMA_MAPPED\fR is returned.
.RE

.sp
.LP
The callback function, \fIcallback\fR, indicates how a caller wants to handle
the possibility of resources not being available. If \fIcallback\fR is set to
\fBDDI_DMA_DONTWAIT\fR, the caller does not care if the allocation fails, and
can handle an allocation failure appropriately. If \fIcallback\fR is set to
\fBDDI_DMA_SLEEP\fR, the caller wishes to have the allocation routines wait for
resources to become available. If any other value is set, and a \fBDMA\fR
resource allocation fails, this value is assumed to be the address of a
function to call at a later time when resources may become available. When the
specified function is called, it is passed \fIarg\fR as an argument. The
specified callback function must return either \fBDDI_DMA_CALLBACK_RUNOUT\fR or
\fBDDI_DMA_CALLBACK_DONE\fR. \fBDDI_DMA_CALLBACK_RUNOUT\fR indicates that the
callback function attempted to allocate \fBDMA\fR resources but failed to do
so. In this case the callback function is put back on a list to be called again
later. \fBDDI_DMA_CALLBACK_DONE\fR indicates either a successful allocation of
\fBDMA\fR resources or that the driver no longer wishes to retry.
.sp
.LP
The callback function is called in interrupt context. Therefore, only system
functions accessible from interrupt context are be available. The callback
function must take whatever steps necessary to protect its critical resources,
data structures, queues, etc.
.SH RETURN VALUES
\fBddi_dma_buf_bind_handle()\fR returns:
.sp
.ne 2
.na
\fB\fBDDI_DMA_MAPPED\fR\fR
.ad
.RS 23n
Successfully allocated resources for the entire object.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_PARTIAL_MAP\fR\fR
.ad
.RS 23n
Successfully allocated resources for a part of the object. This is acceptable
when partial transfers are permitted by setting the \fBDDI_DMA_PARTIAL\fR flag
in \fIflags\fR.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_INUSE\fR\fR
.ad
.RS 23n
Another I/O transaction is using the \fBDMA\fR handle.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_NORESOURCES\fR\fR
.ad
.RS 23n
No resources are available at the present time.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_NOMAPPING\fR\fR
.ad
.RS 23n
The object cannot be reached by the device requesting the resources.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_TOOBIG\fR\fR
.ad
.RS 23n
The object is too big. A request of this size can never be satisfied on this
particular system. The maximum size varies depending on machine and
configuration.
.RE

.SH CONTEXT
\fBddi_dma_buf_bind_handle()\fR can be called from user, kernel, or interrupt
context, except when \fIcallback\fR is set to \fBDDI_DMA_SLEEP\fR, in which
case it can be called from user or kernel context only.
.SH SEE ALSO
.BR ddi_dma_addr_bind_handle (9F),
.BR ddi_dma_alloc_handle (9F),
.BR ddi_dma_cookie_get (9F),
.BR ddi_dma_cookie_iter (9F),
.BR ddi_dma_free_handle (9F),
.BR ddi_dma_getwin (9F),
.BR ddi_dma_ncookies (9F),
.BR ddi_dma_sync (9F),
.BR ddi_dma_unbind_handle (9F),
.BR buf (9S),
.BR ddi_dma_attr (9S),
.BR ddi_dma_cookie (9S)
.sp
.LP
\fIWriting Device Drivers\fR
.SH NOTES
If the driver permits partial mapping with the \fBDDI_DMA_PARTIAL\fR flag, the
number of cookies in each window may exceed the size of the device's
scatter/gather list as specified in the \fBdma_attr_sgllen\fR field in the
\fBddi_dma_attr\fR(9S) structure. In this case, each set of cookies comprising
a \fBDMA\fR window will satisfy the \fBDMA\fR attributes as described in the
\fBddi_dma_attr\fR(9S) structure in all aspects. The driver should set up its
\fBDMA\fR engine and perform one transfer for each set of cookies sufficient
for its scatter/gather list, up to the number of cookies for this window,
before advancing to the next window using \fBddi_dma_getwin\fR(9F).
